This invention relates to apparatus especially, but not exclusively for use in pipe testing and more particularly pressure testing of pipeline welds.
Pipelines to the type used to carry oil and gas often travel long distances and are subject to many potentially damaging effects both externally, from environmental effects, and internally, from substantial pressure effects. Clearly the nature of the transported material is such that leaks are not acceptable. There is thus a need to carry out testing of the integrity of the pipeline at certain points particularly joins or welded repair joints. This requires the use of appropriate pressure testing apparatus.
The pressure testing apparatus used is required to seal off the section of pipeline containing the join or weld to be tested so that pressure may be applied to that area.
The nature of the pipeline is such that any such pressure testing apparatus must be able to deal with two particular difficulties. These are the tendency of long lengths of pipeline to acquire a degree of ovality and the corrosive effect of the oil or gas on the internal surface of the pipeline which can become rough and pitted.
Previously proposed testing apparatus has attempted to overcome these difficulties by using resilient material seals which are forced into the gap between the exterior of a testing device and the interior surface of the pipeline to take up any ovality or surface imperfections.
A known problem of such an approach is that the seal in being forced into the gap between the body of the testing device and the pipeline, and additionally acted upon by the high pressure of the testing may become damaged. As a result the testing device requires frequent maintenance and repair.
A solution to this problem is proposed in GB2242530 where a sealing element is proposed which as outer and inner portions of varying degrees of resilience and deformability. The outer section is relatively soft, so as to deform to the contours of the pipeline, but the inner section is harder so that the overall deformability of the seal is limited. The seal is pushed against a cam slope by a thrust member acting axially so that the seal is deformed radially.
While this development goes some way to overcoming the previously identified difficulties it has limitations of its own. The limited deformability of the two part seal effectively places very narrow limits on the working diameter of the apparatus. The manner in which the seal is thrust against a cam surface to deform its surface against the pipe can lead to it becoming effectively stuck in position when the axial force of the thrust member is removed.
It is an object of the present invention to provide pressure testing apparatus which addresses these identified difficulties.
According to the present invention there is provided pipe testing apparatus comprising an elongate tester body having resiliently deformable pipe sealing means at an end portion thereof and actuator means arranged to resiliently deform said sealing means radially outwardly on activation thereof characterised in that an outwardly angled thrust face on said actuator engages a co-operating inwardly angled thrust face on said seal means in operation and further characterised in that further resilient means are provided to bias said actuator axially away from said seal means on deactivation of said actuator means.
Preferably said sealing means is composed of a nitrile rubber compound.
Most preferably said nitrile rubber compound has a shore hardness in the range of 60 to 90.
Preferably also said actuation means is a hydraulically operated piston assembly.
Preferably also the thrust faces on said actuator means and said seal means are arranged at 45xc2x0 to the longitudinal axis thereof.
Preferably also the further resilient means is a rubber spring.
Alternatively the further resilient means may be a coil spring.
Preferably also said further resilient means acts between said actuator means and said seal means to bias them apart.
Preferably also a pair of said pipe sealing means are provided at either end of said tester body to form a pressure testing area.
Preferably means are provided for applying hydraulic pressure to said pressure testing area.